The present invention relates to a metal cutting insert that is primarily intended for turning operations.
For all sorts of turning operations, there is a certain interplay between the feed rate and the corner radius, the corner radius being the connection between the main cutting edge and the secondary cutting edge. The surface fineness produced on the workpiece is specifically influenced by the interplay between the corner radius and the feed rate. The approach angle is defined as the angle between the main cutting edge and the direction of feed. This angle has a considerable influence on the interrelation between the different cutting force components, and thereby also on the surface fineness and dimension accuracy. Surface fineness and dimension accuracy are very sensitive to changes of the approach angle. One problem for all turning operations is to obtain the desired surface fineness. Another problem is short tool life due to for example crater wear.
It is desirable to provide a cutting insert that improves the fineness of the machined surface.
It is desirable to provide a cutting insert that significantly improves tool life.
It is desirable to provide a cutting insert that improves surface finish over the total tool life.
It is desirable to provide a cutting insert that increases compressive residual stresses in the work piece subsurface.
It is desirable to provide a cutting insert that increases hardness in the workpiece rim zone.
It is desirable to provide a cutting insert that reduces the sensitivity of a turning cutting insert relative to the positioned approach angle.
It is desirable to provide a versatile cutting insert.
In accordance with an aspect of the present invention, a cutting insert for turning comprises an upper surface, a lower surface substantially parallel with the upper surface, and at least three side surfaces extending between the upper and lower surfaces, a transition between two adjacent side surfaces forming a rounded nose radius surface at a cutting insert corner, a peripheral land bridging the upper surface and side surfaces at least at the corner portion at a chamfer angle, and an intersection of the land and the nose radius surface forming a nose cutting edge, the nose cutting edge being defined by at least one radius, the cutting corner comprising at least one curved wiper edge, wherein the chamfer angle in a cross-section at the nose cutting edge is smaller than the chamfer angle in a cross-section a distance away from the nose cutting edge and the chamfer angle has a minimum at a bisector of the corner portion.